Plant-mediated gold nanoparticles as sustainable photothermal nanotherapeutics for melanoma treatment

Melanoma is an aggressive form of skin cancer that often exhibits resistance to conventional therapies, highlighting the need for alternative treatment strategies. In this study, Dicoma anomala ( D. anomala ) leaves methanolic extract was utilized as a natural reducing, capping, and stabilizing agent for the green synthesis of gold nanoparticles (AuNPs). The use of this medicinal plant extract offers an eco-friendly alternative to conventional chemical synthesis methods, as its bioactive phytochemicals can assist in nanoparticle formation while reducing the need for harsh chemical reagents. The plant-derived compounds present in the extract likely contributed to the reduction of gold ions and the stabilization of the formed nanoparticles. The synthesized AuNPs were subsequently characterized to confirm their successful formation, stability, morphology, surface properties, and suitability for further biomedical evaluation. These characterization techniques verified the successful synthesis of AuNPs and provided evidence of their structural features, surface properties, morphology, and colloidal stability. Following irradiation with a 525 nm laser at a fluence of 10 J/cm 2 , the AuNPs demonstrated moderate photothermal activity accompanied by a marked ∼3.5-fold elevation in intracellular reactive oxygen species (ROS), triggering mitochondrial-mediated apoptosis in melanoma cells. In vitro evaluation using A375 human melanoma cells including MTT assays, ROS detection, and live/dead fluorescence imaging demonstrated a clear dose-dependent cytotoxic response. Further mechanistic insights from fluorometric analysis of caspases-3, -8, and -9, along with ELISA-based cytochrome c quantification, confirmed the activation of apoptosis via mitochondrial pathways. Overall, these findings indicate that D. anomala -mediated AuNPs represent a sustainable, effective, and targeted photothermal agent for the treatment of melanoma, with potential to overcome the limitations of existing treatments.